1. Field of the Disclosure
The invention concerns an improved procedure for the sulfation or sulfonation of sulfatable or sulfonatable organic substances and for performing rapid, highly exothermic gas/liquid reactions in conventional thin-layer falling-film reactors, for example, tubular reactors or annular-gap reactors, characterized by the fact that the introduction of the SO3/air mixture is performed according to the invention through several feed locations within (along) the reaction tube or reaction tubes or in the annular gap of annular-gap falling-film reactors.
2. Brief Description of Related Technology
The sulfation or sulfonation of organic compounds is carried out according to current methods which consist in reacting the liquid organic starting materials with the gaseous mixtures containing SO3 (for example, with conversion gas, a.k.a. converter gas). The sulfonation or sulfation reactions are highly exothermic so that, together with high local sulfur trioxide concentrations in the reaction mixture, production of oversulfonated and oversulfated products and undesirable side reactions occur, which have a considerably adverse influence on product quality.
A procedure is described in DE 2 621 455 in which, in a special mixing reactor, the organic substance to be sulfonated flows together with undiluted liquid or gaseous sulfur trioxide under turbulent mixing conditions, the reaction mixture is cooled outside the reactor, and is reintroduced into the mixing reactor. The yield and color of the reaction product are unsatisfactory.
Patent Publication DE 1 443 500 describes a device for continuous sulfonation of organic substances, the device consisting of several mixers from which the reaction mixture is passed from the previous into the next reactor with intermediate cooling and whereby here, too, dilute SO3 is added. This method does dose the SO3 in two steps, that is, in the first step in a less than stoichiometric amount, but this reactor system is technically expensive and has not found application either.
U.S. Pat. No. 3,482,947 describes a single-tube or multi-tube film reactor in which the raw material to be sulfonated is applied uniformly through a liquid reservoir to the inside surfaces of the reaction tubes in which another tube with a smaller diameter is located, so that an annular gap is formed, whereby the liquid is applied uniformly as a film into the reaction tube. The dilute SO3 gas is introduced inside this inserted tube. The raw material film to be sulfonated comes into direct contact with the spontaneously reacting diluted SO3 gas. This leads to local oversulfonation, that is, a large excess of SO3 is offered to the film surface or to the liquid drops that have been formed on the surface. This leads to undesirable side reactions and to a worsening of the color of the reaction product.
In U.S. Pat. No. 3,667,919 a reactor head is described for a falling-film annular-gap sulfonation reactor with which it is possible to dose the organic raw material on the inner surface of the outer reaction tube and on the outer surface of the inner reaction tube separately. In this way, supposedly a film with uniform thickness, corresponding to the inner and outer diameter is produced, in order to avoid an excessive supply of SO3 to the thinner film. With this method, too, the organic material and the SO3 are brought together simultaneously, as described above, which results in oversulfonation with the disadvantages of side reactions and poor color.
In U.S. Pat. No. 3,169,142 a device is described in which in a film tubular reactor the liquid to be sulfonated is applied as a film to the inner wall and the diluted SO3 gas is introduced through a nozzle into the inner tube. The outer wall of the tube is cooled and serves to remove the heat generated in the extremely fast exothermic reaction. Practically, the device is limited to only one tube; a uniform distribution both of the organic raw material as well as of the dilute SO3 gas is not described. Here too the organic raw material and the SO3 gas are brought together simultaneously, which, because of the local excessive concentration of SO3, results in the occurrence of undesirable side reactions. Also, the temperature increases greatly because of insufficient removal of heat, which again promotes side reactions and leads to a worsening of the color of the reaction product. This device has not been used in practice either.
In Patent Publication DE 2 923 510 a method is described for the sulfonation of alkylated aromatic hydrocarbons in which the organic raw material is atomized in a special reactor (in the literature known as CHEMITHON Jet Impact Reactor) to produce a large surface, and the fine droplets formed can react with the SO3. The finely distributed droplets of the reaction mixture are mixed intensively with cooled, recycled sulfonic acid (reaction mixture) that has been degassed in a cyclone and thereby cooled (quenching). The method has the disadvantage that the product stream is not cooled on the way from the reactor to the cyclone separator (separation of gas/liquid) and therefore the temperature increases greatly. This leads to darker products in comparison to the falling-film reactors in which the cooling begins directly during the reaction through the outer cooling surface. Therefore, this type of reactor is used only where the product color is of lesser importance.
In U.S. Pat. No. 4,335,079, film sulfonation is described in which the film is applied to the inside surface of a rotating sphere and the SO3 gas is introduced to the film through various zones. However, the thickness of the film is not uniform enough, so that uniform sulfonation does not occur. Besides, the apparatus is too complicated and therefore it has not been applied in practice.
In “Sulfonation technology in the detergent industry”, Kluwer Academic Publishers (1991), Dordrecht, Netherlands, Herman de Groot, W., p. 148, the CHEMITHON falling-film reactor is described as it is used today in the detergent industry. In this method too, the organic raw material and the SO3 are combined simultaneously as described above, which leads to oversulfonation, with the disadvantages of side reactions and poorer color. Also, after a relatively short time, crusting is formed in the upper reaction zone. Cleaning of the reactor is necessary, which leads to production losses.